During standing or walking, a repeated load is continuously applied in excess to the foot region due to deformations and the like of the skeletal structure. When this occurs, so-called hallux valgus, flat foot, and other alignment abnormalities and lower extremity ailments are brought about, and if the symptoms worsen, then walking itself becomes difficult and other important problems occur that make a person unable to sustain daily life. The skeletal structure and form of the foot have therefore been analyzed, and a variety of sole inserts and footwear have been proposed with the purpose of preventing and treating functional failures of the foot region.
For example, footwear has been proposed in which the emphasis is on the direction of movement of the load on the foot region during walking and which can be used in the treatment and prevention of lower extremity ailments according to an original theory (see Patent Document 1). Shoes and shoe sole inserts have also been proposed in which the arch structure of the foot region can be regulated and the function of the foot can be reinforced (see Patent Document 2). A variety of other footwear and sole inserts have been proposed according to analyses of the skeletal structure of the foot.
Patent Document 1: JP-A 2005-347
Patent Document 2: JP-A 9-224703
It is, however, impossible to find a radical solution unless a solution strategy is adopted based on the fundamental concept and function of the foot region, despite the fact that a variety of resolution means have been proposed with the purpose of preventing and treating hallux valgus and other alignment abnormalities and functional failures of the foot region in the footwear and sole inserts proposed in the past.
As shown in FIGS. 6(a) and 6(b), the foot region of a human being is constructed from many bones, functions in an intricate manner, and is formed into an arch structure so that force resulting from adaptation to uneven terrain and from body weight and body movement is transmitted to the surface. It is generally assumed that the arch structure comprises an internal longitudinal arch (an arc in which the navicular is at the peak, the rear starts from the point of contact with the calcaneus, and the front is made from the first metatarsal), an external longitudinal arch (an arc in which the cuboid is at the peak, the rear starts from the point of contact with the calcaneus, and the front is made from the fifth metatarsal), and a lateral arch (an arc made from the metatarsals), as shown in the drawings. The main role of the foot region is believed to be to distribute loads and absorb shock to the sole, hoist up the arch using a windlass structure, and move body weight using lever action.
However, past methods of thinking about the arch structure and knowledge of the role of the structure have been based on observations of one portion of the foot region, and cannot be regarded to take into account the fundamental functionality of the foot region. In other words, in anthropoids other than humans, the configurations of the hands and feet are similar, and the feet can perform the motion of grasping an object in the same manner as the hands. Even though human feet originally had a catching function for grasping objects in the same manner as the hands, humans started bipedal walking, the structure of the foot evolved to suit bipedal walking, and a decline in the catching function was caused by the birth of footwear. Therefore, in order to comprehend the fundamental functionality of the foot, observation should be returned to the original structure of the foot that could grasp objects.
When the human foot region is considered from an anatomical point of view, a structure exists that is capable of a grasping motion using the closing motion of the thumb and four toes, and the bending motion from the MP joints. When looking at the wrinkles of the sole, the biggest wrinkle exists in the long axial direction to the side of the ball of the thumb, and this wrinkle exists in a portion that, functionally, can perform bending in the same manner as seen in the hand. For this reason as well, the fundamental function of the human foot is in the grasping motion, and the above-mentioned past concept of the arch of the foot should also be considered based on the fundamental concept of the function of the foot region itself. The line that links the cuboidal bone edges and the cuneocuboid joint areas with the second and third MP joint areas, which form the basis of the grasping motion, should be thought of as the functional fundamental arch. This is because the fundamental arch forms a peak, the above-mentioned internal and external longitudinal arches are disposed to the left and right of the fundamental arch, and these arches would not be established without this peak.
Measures designed to solve the problems of hallux valgus, flat foot, and other alignment abnormalities and functional disorders of the foot region differ widely depending on whether the foundation of the foot region is perceived as a structure for grasping or whether it is perceived simply as a structure that collapses like a spring. To find a radical solution to the problems of the foot region, it is first necessary to promote the original function and motion of grasping in the foot region, whereas the products proposed in the past were not configured based on such a fundamental function and motion.
The present invention was therefore perfected in view of the fact that a radical solution can be expected to be found for alignment abnormalities and functional failures by being able to perform the heretofore ignored above-mentioned fundamental motion based on the form of the functional fundamental arch line that links the cuboidal bone edges and the cuneocuboid joint areas with the second and third MP joint areas of the foot region, and an object of the present invention is to provide a footwear sole insert and footwear that can regulate and promote the form of this arch.